textproduct: Quad Cities

KEY MESSAGES

- Temperatures are expected to be slightly above normal to finish October.

- A large storm system is expected to impact the region Tuesday through Wednesday, bringing the next chances of widespread rainfall to the region, along with windy conditions Tuesday night through Wednesday, with gusts over 30 mph possible.

- Rainfall totals with the Tuesday/Wednesday system have come down slightly, but are likely to range from around 0.25-0.50 inches over northwestern Illinois to around 0.90 inches or more along and south of a Fairfield to Burlington line.

SHORT TERM /THROUGH TONIGHT/

Issued at 150 PM CDT Mon Oct 27 2025

High pressure continues to sit to the northeast resulting in east winds of 10 to 20 MPH and gusts up to 25 MPH. Temperatures at 2 PM range from 59 degrees at Dubuque to 64 degrees at Macomb.

High pressure is forecast to move into western Ontario tonight as a shortwave trough digs into the Plains and begins to strengthen. Moisture aloft is forecast to slowly increase tonight causing clouds to move into the area and thicken overnight. Winds are forecast to remain easterly at 5 to 15 MPH. The increase in cloud cover will allow temperatures to be warmer than last night with lows ranging from the upper 40s in far southeast Iowa and northeast Missouri to the lower 40s in far northwest Illinois.

LONG TERM /TUESDAY THROUGH MONDAY/

Issued at 150 PM CDT Mon Oct 27 2025

The Pacific NW longwave trough is progged to arrive on Tuesday, with chances of rain increasing after 12z/7 AM Tuesday morning but may hold off until after 18z/1PM depending on how quickly saturation takes place. Model Time/Heights show low level dryness lingering across the area especially the northeast half or northeast of a line from Cedar Rapids to the Quad Cities to Galesburg. CAMs also suggest that it will take a little bit of time for the column to saturate, so only our western CWA could see light rain before expanding eastward. Eventually, as large- scale lift increases and an attendant surface cold front begins to move in, moisture ahead of the boundary looks to increase as Pwats between 0.8" to 1.0" per the HREF ensemble mean. Much of the global deterministic and LREF cluster analysis ensemble members agree on a cut-off upper low developing just south of our region, meaning a slower, stronger system is likely to develop. Moisture appears to be favorable to linger across our southern CWA due to this evolution. NBM exceedance probabilities of total rainfall of a half inch Tuesday/Wednesday ranges from 30-50% across our northeast to 60-80% across our southwest. Given the dry conditions we've had lately and expanding drought, this will be beneficial rainfall. A large gradient in rainfall totals from eastern Iowa into northwest Illinois is possible with this storm system with dry air being pulled into the system especially in far northwest Illinois, north of Highway 30 where less than a quarter of an inch of rain is possible and parts of Stephenson County may see less than a tenth of an inch. Areas west of a Fairfield to Macomb line could see between 0.6 and 0.90 inches which is slightly lower than previous forecasts.

The other aspect of this upcoming system will be a tightening pressure gradient and deeper boundary layer mixing on Wednesday, which should support gusty conditions. The 50th percentile of the NBM for peak wind gusts is ranging between 30 to 40 mph, so something we will need to keep an eye on as we get closer to Wednesday. Will these winds reach Wind Advisory criteria? At this time, it doesn't appear likely, given the LREF probabilities of gusts 40 mph or stronger are only around 10 percent.

Eventually, the trough will exit the region by Thursday, making way for a period of calmer weather through the upcoming weekend. A cooler air mass will result in some chilly nights for Wednesday night through the end of the week, with lows in the 30s each night. Daytime highs will continue to be in the 50s. Beyond Friday, models show deep northwest flow aloft with the potential for disturbances passing to our north and east to clip the area and bring low chances for rain showers on Saturday and Sunday.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 630 PM CDT Mon Oct 27 2025

High confidence exists on VFR conditions through 28/12z. 28/12z-28/21z high confidence on VFR to MVFR conditions (mainly ceilings). Between 14z-21z anticipate some stratus and areas of MVFR ceilings to develop from south to north at the terminals as S/SE flow in the 1-3kft agl layer ahead of an approaching system advects stratus /currently in downstate IL and IN/ into the region. Some uncertainty does exist with the northward extent of the MVFR ceilings, particularly at KDBQ as the flow is more easterly, and it may not be until the very end of the TAF period or just beyond before conditions deteriorate there and that's how I opted to go with the TAF at KDBQ. Elsewhere, I introduce MVFR ceilings 2-3kft agl initially at KBRL around 15z and then into KCID and KMLI after 18z through 22z. Some spotty light rain/sprinkles may also accompany the stratus with little/no impact on visibility. Toward the end of the TAF period (28/21z) and beyond through 29/06z, anticipate more widespread light to moderate rain and MVFR to IFR conditions becoming prevalent. Winds will remain easterly throughout the TAF period, sustained around 8-15 kt. Gusts 20-25+ kt are expected to develop at KMLI and KDBQ after 28/18z-21z.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.